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Black Holes Encyclopedia

RX J1242-11

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In the constellation Virgo

Finder Chart


700 million light-years


100 million times the mass of the Sun


Greater than the size of the asteroid belt in our solar system

Discovery Methods


RX J1242-11

In the heart of the distant galaxy known as RX J1242-11, a star similar to the Sun apparently suffered a violent and dramatic fate. After a close encounter with another star changed its orbit, the star passed quite close to a black hole that may be 100 million times as massive as the Sun. As the star approached this dark monster, the black hole exerted an ever-stronger gravitational grip on the star. The side of the star closest to the black hole was pulled more strongly than the side away from the black hole. This "tidal gravity" (like the effect that causes ocean tides on Earth) stretched the star and eventually ripped it apart. Some of the star's hot gas was ingested by the black hole, while the rest was thrown clear. The remaining gas formed a long, glowing streamer.

Astronomers discovered the star's violent end by watching the galaxy with two orbiting X-ray telescopes in 2002. Both telescopes observed bright outbursts of X-rays as some of the star's gas encircled the black hole. The Chandra X-Ray Observatory determined that the outburst came from the region in the galaxy's core. XMM-Newton measured the spectra of the event and the space around it, which helped astronomers determine that there were no other major forces at work to produce the outburst. The combined data confirmed that a supermassive black hole inhabits the core of RX J1242-11, and helped astronomers estimate its mass.



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This document was last modified: March 3, 2011.


RX J1242-11
Artist's Rendering

Artist's Rendering


RXJ 1242
Animation of star ripped apart by RX J1242-11's black hole.